Northumbrian Water reveals Microbial Electrolysis Cell trials
Northumbrian Water and Newcastle University have carried out the first trial of a hydrogen Microbial Electrolysis Cell (MEC) on real sewage at a wastewater treatment works on Tyneside.
Speaking recently at the British Science Festival in Newcastle, experts from Northumbrian Water and Newcastle University revealed how they have harnessed the power of the billions of naturally-occurring microbes in sewage. The process has shown that not only can wastewater treatment plants be completely self-powered and the treatment process improved, they can also be used to produce significant quantities of hydrogen gas, which could be collected and used to power electric vehicles, for instance.
MECs are the next generation of microbial fuel cells. In the Newcastle design, each MEC is composed of a number of removable “cassettes”, each of which is made up of carbon felt trapped between metal meshing and connected to a positive and negative electricity supply.
As the raw sewage is pumped through the cell, the microbes growing on the carbon felting strip the electrons off the sewage and transfer these to the anode, producing electricity.
Meanwhile the hydrogen ions that are left migrate to the cathode where they are reunited with the electrons that have been topped up with just enough energy to allow them to turn the hydrogen ions into hydrogen gas. The energy required to top-up the electrons is less than the energy released. So the system is potentially energy positive.
Funded by the Engineering and Physical Sciences Research Council (EPSRC), the team now plan to install the next generation of MEC at a wastewater treatment works in Sedgefield, County Durham.
Northumbrian Water is one of the leading companies in the water industry that has been developing anaerobic digestion, with its £70M advanced anaerobic digestion (AAD) plants at Howdon on Tyneside and Bran Sands on Teesside. All the sludge remaining once the wastewater from 2.6 million customers in the North-east has been treated is producing gas that is being turned into electricity.
This new MEC system takes this to the next level. Using raw, untreated wastewater at normal temperatures, the entire process is fuelled using the energy from bugs.
Tom Curtis, Professor of Biological Engineering at Newcastle University, said: “Wastewater contains two to three times more energy than we use to treat it so if we can harness that energy we can not only close the loop on sewage treatment to create a totally self-treating system, we will also have spare energy to use elsewhere.
“What’s really clever about this system is that it works on raw sewage at ambient temperature. Most anaerobic digesters require a high-energy, concentrated food source and heat to work properly which means the water has to be removed first and this is an energy-expensive process.
“What we have developed is a system that feeds on the waste as it arrives at the plant – the whole lot goes in and the microbes do all the hard work.”
Maxine Mayhew, commercial director for Northumbrian Water, said: “As the industry leader for generating sustainable power from poo it’s a natural progression for us to look to science to see what more can be achieved in the future. Currently we are harvesting the methane released by bacteria as they digest the sludge which is then used in gas engines to create electricity.
“Now, in another innovative move to maximise the energy production, we are working to upgrade and purify the biogas so it can be directly injected into the gas grid.
“As industry pioneers of generating power from wastewater we now look to our work with Newcastle University to take this energy production to another level and develop production of hydrogen - the clean fuel of the future.”
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